diff --git a/config/filter.d/squid.conf b/config/filter.d/squid.conf
index 8cbf744f..da282692 100644
--- a/config/filter.d/squid.conf
+++ b/config/filter.d/squid.conf
@@ -4,7 +4,7 @@
 
 [Definition]
 
-failregex = ^\s+\d\s<HOST>\s+[A-Z]+_DENIED/403 .*$
+failregex = ^\s+\d\s<HOST>\s+[A-Z_]+_DENIED/403 .*$
             ^\s+\d\s<HOST>\s+NONE/405 .*$